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[noo-klee-uh-luh s, nyoo-] /nuˈkli ə ləs, nyu-/
noun, plural nucleoli
[noo-klee-uh-lahy, nyoo-] /nuˈkli əˌlaɪ, nyu-/ (Show IPA).
Cell Biology.
a conspicuous, rounded body within the nucleus of a cell.
Origin of nucleolus
1835-45; < Late Latin: small kernel, equivalent to nucle(us) kernel (see nucleus) + -olus -ole1 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for nucleolus


noun (pl) -li (-laɪ)
a small rounded body within a resting nucleus that contains RNA and proteins and is involved in the production of ribosomes Also called nucleole
Derived Forms
nucleolar, nucleolate, nucleolated, adjective
Word Origin
C19: from Latin, diminutive of nucleus
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for nucleolus

1845, from Latin nucleolus, literally "a little nut," diminutive of nucleus (see nucleus).

Online Etymology Dictionary, © 2010 Douglas Harper
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nucleolus in Medicine

nucleolus nu·cle·o·lus (nōō-klē'ə-ləs, nyōō-)
n. pl. nu·cle·o·li (-lī')
A small, typically round granular body composed of protein and RNA in the nucleus of a cell, usually associated with a specific chromosomal site and involved in ribosomal RNA synthesis and the formation of ribosomes.

nu·cle'o·lar (-lər) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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nucleolus in Science
Plural nucleoli (n-klē'ə-lī')
A small, typically spherical granular body located in the nucleus of a eukaryotic cell, composed largely of protein and RNA. When the cell is not undergoing division, loops of DNA from one or more chromosomes extend into the nucleolus and direct the synthesis of ribosomal RNA and the formation of ribosomes. The ribosomes are eventually transferred out of the nucleus via pores in the nuclear envelope into the cytoplasm.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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